Police chiefs in Northern Ireland have apologised to a former officer badly injured in a dissident republican bomb attack.

PSNI constable Peadar Heffron suffered serious injuries when the undercar booby trap device was detonated near Randalstown in Co Antrim five years ago.

The Policing Board, which oversees the service, expressed concern after an investigation found four officers had failed to give information to detectives investigating the attempted murder of a colleague. The service imposed a lower disciplinary sanction on two of the intelligence officers than recommended by an independent watchdog.

Chair Anne Connolly said: "During discussions, board members also sought assurances around the support being provided to Peadar Heffron and very much welcome that he has now received an apology from the PSNI."

Chief Constable George Hamilton and his deputy, Drew Harris, met Policing Board members in a private session on Tuesday.

Catholic constable Heffron was a target for dissident republicans opposed to the peace process who want to deter Catholics from joining the force.

He is an Irish language speaker and captained the PSNI gaelic football team.

The officer's leg was amputated after the device exploded in 2010 and he has since left the force.

Ms Connolly added: "Board members are of the view that the PSNI decision to reduce the sanctions recommended by the (Police Ombudsman) sends a negative message on the jurisdiction of the office and the necessity for police officers, whilst recognising the rights of officers to due process, to fully cooperate with investigations."

Even though there was insufficient evidence to support an allegation that the attack could have been prevented, Police Ombudsman Dr Michael Maguire said there was a failure to help detectives investigating the blast.

Four officers, two detective superintendents and two detective sergeants, from the PSNI's C3 unit should be disciplined, the Ombudsman said.